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Ch14: Principles of Disease and Epidemiology

Terms in this set (74)

Infection
invasion of the body by microorganisms
disease
host becomes ill
pathology
study of disease
etiology
cause of disease
pathogenesis
development of the disease (signs & symptoms)
normal microbiota
babies are sterile in utero, gains Lactobacilli in intestines as baby passes through the birth canal
transient
short
microbial antagonism
normal microbiota prevent colonization by pathogenic species
microbial : vagina
bacterial microbiota of the vag keep it nicely acidic. Antibiotics kill these off, resulting in susceptibility to yease infections caused by Candida albicans
microbial : mouth
normal streptococci prevent growth of pathogenes, especially fungi and Candida albicans
microbial : colon
Normal E. coli in the large intestine prevents growth of salmonella and shigella. If normal microbiota is reduced, can cause Clostridium
microbial: skin
staph epidermidis prevents overgrowth of pathogenic bacteria or yeast
Probiotics
supplements that contain "good" bacteria that can outcompete pathogenic bacteria
pasteurization
heat product rapidly Good-- saves life, long shelf life Bad-- kills probiotics
what do probiotics do?
can prevent and treat wound infections (lactobacillus)by 100%, and E. coli injected into patients with recurring bladder infections can prevent it for 1 yr
Symbiosis
Normal microbiota and host live together
Mutualism
both host and microorganism benefit
Commensalism
microbe benefits; host not harmed
Parasitism
microbe benefits; host is harmed (diseases)
Koch
discoved the microbes that cause anthrax(bacillus) and TB (M. tuberculosis)
Koch's Postulates
1.Microbes present in every case 2.Microbe must be isolated & grown in culture 3. Microbe cause disease when injected into susceptible host 4.Microbe sample from sick/dead can grow in culture and identical to culture in step 2
Kock's Postulates Problems/Exceptions
1.Some microbes do not grow well in a culture and need to be in a host cell (viruses, leprosy) 2. Symptoms can be caused by several different kinds of organisms (PNEUMONIA-- h.pneumonia, s.pneumonia, viral pnneumonia) 3. The same organism can cause several different diseases (streptococcus {pyo}genes--strep throat, scarlet fever, flesh-eating disease[necrotizing fasciitis])
Opportunistic Microorganisms
organisms that do not normally cause disease in their normal environment, but can if gain access elsewhere (E.Coli--UTIs, lung infections)(Streptococcus pneumoniae or meningitidis)
Communicable disease
passed from one host to another (HIV)
Non-communicable disease
(vector or fomites) not passed from one host to another (tetnis--back in the ground, step on nail) (malaria--bug bites person, has it, bites you)
Decribing Diseases: Signs
(objective) measurable (temp, vomitting, diarrhea, rash)
Decribing Diseases: Symptoms
(subjective) not measurable (Pain, nausea)
Decribing Diseases: Syndrome
group of signs/symptoms appear together, but not all are always present
contagious disease
communicable disease that is spread easily
Occurrence of a disease: Incidence
number of people in a population who develop a disease in a period of time
Prevalence
number of people who have the disease in a period of time (going to be bigger)
Endemic
always present in a population (eg. common cold)
Epidemic
sudden outbreak in a population (influenza, AIDS)
Pandemic
sudden outbreak worldwide
Acute
sudden onset, short duration (cold, flue)
chronic
slow developing, long-lasting (bronchitis, mono, hepatitis, TB, herpes)
Latent
infection does not become "active" for possibly many years--"hides" and waits for opportune time(during stress/immunesuppression) (HIV, shingles)
herd immunity
when many people in a population are immune to a particular disease (chicken pox)
Local infection
in one spot (pimple, wart, boil)
Systemic(generalized) infection
able to move in the blood, whole body is affected (influenza)
Focal infection
infection starts in one place, then moves. (strep in the mouth can move in blood stream and to heart valves[ endocarditis]) Can occur @ dentist(bacteremia)
propholactics
protection / antibiotics (before dental visit)
sepsis
blood poisoning (bacteria multiplying in the blood) (Staph aureus in blood from IVs, catheters, trainage tubes)
septic shock
organ failure resulting from sepsis (50% mortality rate) Staph aureus
Toxemia
bacteria toxins in the bloodstream
Viremia
miruses in bloodstream
Primary Infection
Comes in first, acute infection(flu, cold, HIV)
Secondary Infection
after initial illness, typically bacterial/fungal (pneumonia is classic example[bronchitus]
Subclinical infection
person carries the pathogen, but does not have symptoms (hep A)
Development of Disease
Incubation Period: no symptoms 2.Prodromal Period: mild symptoms 3. Period of Illness: disease is acute and patient may die 4. Period of decline: symptoms lessen 5. Period Convalescence: recovery (still contagious)
Reservoirs of infection
source for the pathogen to live and thrive
Human reservoirs
people with or without symptoms
Animal: zoonoses
disease from animal to human (vector) (rabies, lyme disease)
non-living reservoirs
soil & water
Transmission of disease: Contact transmission
direct (hand-shake) indirect, droplet--sneeze, cough (doorknobs or other object involved in spreading of disease=fomites)
Vector
animals that carry pathogens from one host to another
How to get nosocomial infections?
1. microorganism present in hospital 2. compromised host [broken skin, suppressed immune] 3. Chain of transmission (staff to patient)
Most common pathogens in nosocomial infections
E. coli, enterobacter, S. aureus, streps, P. aerginosa,{ not washing hands, poor aseptic technique}
Biofilms: 40% Nosocomial infections are caused by these...
many species of bacteria live in layers together, protecting one another from antibiotics/bleach
Capsules
avoid phagocytosis by host-- most bacterial pathogens that make us sick possess a capsule (S. pneumoniae, Bacillus, S. epidermidis) capsules make bacteria slippery and hard to engulf
Invading
adhering to host, avoid our immune system
Damaging host cells...
direct: damage cell membrane 2. indirect: cause overreaction of our immunesystem
streptococcus mutans
sticky glycocalyx on the teeth, allows actinomyces to also thrive
Mycobacterium
Hids from immune system in our cells. Has a waxy cell wall and avoid phagocytosis. Don't die if engulfed by white blood cells, may reproduce in WBC.
1/3 the world is infected by....
M. tuberculosis. More human deaths than any other bacterium.
Strep pyogenes
Neisseria meningitidis = gonorrhea
IgA proteases--defences where and what it does?
In the cell wall, prevents adherence to mucous membranes by bacteria (Neisseria can break down this defence and adhere)
Can hide inside a clot in the body...
Staph aureus
fimbriae
some bacteria have fimbriae that helps them attach and endocytosed (taken in) by our cells (E. coli, shigella, listeria)
What two bacteria can harness our actin and use to propell to other cells?
Listeria & Shigella
Speedy & Spreading through tissue remains ahead of WBC (this breaks down connective tissue....?
S. pyogenes--necroticing fasciitis and clostridia--gangrene
Bait & Switch....what do bacteria use for this?
antigens (ID tags) same bacteria will switch its antigens so our immune system won't recognise anymore and can reinfect over and over. (flu)
Endotoxins are commonly gram...?
negative
Exotoxins are commonly gram...?
positive (clostria, s. aureus) Neurotoxins=clostridia=botulism, tetanus
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